Magnetically Inert Knives

C

Compact

Joined
Oct 11, 1998
Messages
76
Lately I have noticed an increase in the number of Magnetically Inert knives on the market. You know, the ones that you can pass through metal detectors at airports without being discovered. I was wondering what people think about this.
Personally, I have zero need for one, but I have thought that before and been proven wrong. What are some good reasons for owning them if you happen to be a run-of-the-mill average Joe like me? (Now I am speaking strictly of practicality reasons. I am an ardent knife collector and have many knives that I have no real "need" for.)
So, what do you think?

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-Compact
:)

 
Myself, I can't think of any advantages most "inert" knives have over steel for "everyday Joe," except perhaps that titanium knives like the Mission series can be unbelievably strong. The composite knives like the MD frequent flyers seem like the kind of thing that might get one in trouble: you have it, you want to put it to use, one day you go through airport or courtroom security with it, by some crazy fluke it is discovered . . . unless you're in law enforcement, you are in for a really really big hassle!! Although I do confess to owning and sometimes carrying a delta dart . . . even knowing that if I use it for self-defense it looks worse than using a mere "pocketknife" for the same purpose. But I digress. There is one inert blade that may have practical, non-spooky advantages over steel blades, but I know very little about it - the Mad Dog Mirage X ceramic-blade series, as described by their literature, sounds tantalizing indeed: "The Mirage X can cut glass and shave steel off of a SEAL A.T.A.K. without going dull." So if anyone knows more about these knives, they might be able to give you an informative answer to your question . . .
 
I have a MD Mirage Micro. Yes it does go through detectors
biggrin.gif
It's a good knife to carry all day under a T-shirt( I live in Hawaii)or in your shorts.mine cuts decently but it won't get razor sharp. The blade is rather thick so cutting into stuff causes it to bind,what I like about it is you can carry it anywhere and not worry about corrosion. I still carry a Sebenza for most tasks and use the Micro as a quick draw weapon.
 
Just for your info there is no such thing as a magnetically inert knife, Period. They have very reduced signatures but are not void no matter what they claim. Airport magnetometers can be adjusted to catch very low signature knives but no one would ever get to a plane. Most of the knives that have a low signature, are very corrosion resistant, and the Ti ones are very light and therefore some people perfer them for that reason. Other than that I can see no reason for anyone to carry a LO-MU knife.



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Blue Skies

 
Rob,
The Mirage series from Mad Dog knives have no steel or metal in them. Period. Correct me if I am wrong, but ceramic composite shouldn't have any mag. signature.

greg
 
Also MD Frequent Flyers are a compound with no metal whatsoever. Not to mention a variety of Carbon Fiber and G-10 knives that have been made.



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Mouse Assassins inc.

 
SB: I've been over on the Custom knives forum, waiting for Mr. Cude to educate us about magnetism.

Mr. Cude; you may do so here, if you please. I am sure the members would like your input about magnetic/non magnetic knives.

I know about magnetic measuring units of Gauss and Oerstads, but Mu is new to me. Please feel free to elucidate and expound; you will find us a grateful audience. I am confused about one point; on the Custom forum you said Ti had a(magnetic)reading of 0. On this forum, you said there is no such thing as a non magnetic knife. If you could possibly clear up my confusion, I would be grateful. Thanks in advance, Walt Welch
 
Mr. Cude; I apologize. The reference to Ti's magnetic characteristics was made on another forum, by another person. I hereby reprint it, so that you may comment on it. I hope I have not caused any inconvenience. Thank you, Walt Welch

missionknives posted 11-20-98 08:29 ET (US)
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Non-magnetic? Don't be fooled.
6K will NOT, I repeat, will NOT pass the LoMu (non-magnetic) tests. We are always looking for other advanced materials and Stellite was an option for us. Got some pieces from Deloro, sent them to the NAVEODTECHCTR and they failed!

Mil-M-19595 permits a 5 gamma reading, this 6K was 220 gamma! Titanium is 0.

Stellite is very magnetic when it comes to infuence mines.

I will post these test results on our website soon.

Rick

 
As to need...sometimes ya just gotta break the law. Other times it's a private company getting all set up to screw you over.

Case in point: years ago my brother was invited to an Oakland (Calif.) rap concert. Not generally his thing (or mine) but it was free, some friends were going, whatthehell.

They set up metal detectors at the doors. Sure enough, the 72nd street gang went on a total rampage (pre-planned) and went running around the upper deck of the Oakland Colliseum, throwing people down the long flights of stairs leading below. My brother and several of his friends helped some guards form a "scirmish line" blocking their path around the upper deck at a chokepoint and together fought a pitched holding action against these jokers while those less able evacuated out behind. We're talking genuine medievel battlefield stuff with every object imaginable being used as weapons.

Total chaos. They haven't approved an indoor rap concert permit in Alameda County since.

You think a Mad Dog MirageX wouldn't have come in REAL FOOKIN' HANDY right about then?!

Jim March
 
Walt,

The tests which Rick talks about are the same tests I conducted at the same facility and at another remote facility. He is true in his statment. Fe content and a magnet not sticking to something have nothing to do or should I say very little to do with the magnetic signature of an item, we have FasTex buckles that fail and they are nylon. Cobalt is Feromagnetic and this is what causes the problems. Hope this answers your questions.

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Blue Skies

 
Canadian laws allow the carrying of non-magnetic grade steel knives. Therefore, based on this fact it is reasonable to assume there is a market for this type of knife. Can someone list the knives that are available with this trait ? Thank you

Regards,

xxxx
 
Cobalt is a brittle, hard, transition metal with magnetic properties similar to those of iron.

cobalt

(Co), chemical element, ferromagnetic metal of Group VIII of the periodic table, used especially for heat-resistant and magnetic alloys.



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Blue Skies

 
Rob,
I'm still confused how a "non-metallic" object would produce a magnetic signature. Plastic? Wood? Other organic materials? Is there some sort of ambient iron content, on an atomic level, that's being picked up? The low Mu also had me scrambling for a handy textbook to learn about it, but the book was to general to reference it. This is really interesting stuff, so any further info would be appreciated.
 
Rob (EOD), see what I started? Glad you're back on line to answer the questions. I didn't even want to try to answer some of them.
I can answer your's Rob S. Even a rare earth magnet won't stick to it.
You'll feel free to "pick his brain", I been doing it for years.
 
Well, I am somewhat closer to enlightenment after chatting with Rob Cude on IRC.

The test has nothing to with the ability to permanently magnetize the object tested. Rather, the test seems to measure the effect of the object on a magnetic field.

This is what is confusing, as most people think that only Fe can be magnetized. Actually, some 'rare earth' magnets are much more powerful than Fe magnets. One such compound is Samarium Cobalt (SmCo), used in expensive stereo speakers.

Cobalt by itself may or may not be able to be magnetized permanently (I have differing data). This is not really relevant, however, as what quality we are measuring is the ability to create eddy currents in a magnetic field. Copper (Cu) is very good at doing this; old auto generators were Cu armatures rotating in a permanent magnetic field. This generated eddy currents, which created electricity. Copper cannot be permanently magnetized.

Some plastics are able to conduct electricity; these have had Co added! This may explain how some plastic items fail the test of whether or not magnetic mines will be affected by the object in question.

Rob said that the units used to determine whether or not an object was safe to use around magnetic ordnance were milioerstads; an acceptable measurement was 0.05 milioerstads, or 5 Gamma.

Oerstads, as it happens, I know to be units which measure an object's coercivity. Coercivity is usually defined as the strength of the magnetic field necessary to change existing magnetic domains. Actually, all of you know this already; magnetic tape is erased by a magnetic field before re-recording. Metal tape has a higher coercivity, which means a stronger magnetic field is necessary to erase it, compared with ferric oxide tape. This also means that the metal (Type IV) audio tape is more resistant to accidental degradation (such as placing the tape next to a speaker, with the strong permanent magnet inside), as again, it takes a stronger magnetic field to change the existing magnetic domains.

Rob further said that the object tested was tested at different distances from the measuring device. From 4 feet to one inch, then in contact with the measuring device.

Trying to make sense out of all these data, I believe what is being tested is the ability of an object to generate eddy currents in a magnetic field. This is certainly consistant with what I have read about magnetic mines, which depend on a disturbance in the earth's magnetic field to be triggered. Eddy currents are certainly magnetic fields which disturb the earth's magnetic field.

Note that neither a pre-existing magnetic field, nor an ability to create a permanent magnetic field in a given substance is required for that substance (Cu for example) to be an excellent eddy current generator.

As always, any input, comments, or criticisms are welcome, as I am still groping through the fog to really understand this. Walt Welch
 
I had no idea when I started this thread that it would generate such great discourse. I feel that I am learning a lot that I wouldn't have ordinarily been exposed to. This is the true value of the forum setting. Questions arise from questions.
Thanks to all so far for the great responses.

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-Compact
:)

 
Yes Compact, this is a great thread, I want to take this opportunity to thank Kit Carson for the several e-mails back and forth. I drew on his Stellite experiance to do a very satisfying project for me and Bob and Doc. And it is great to have the Co-Designer of the U-2/Intrepid giving us his valuable input here. Keep it up guys and gals!

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www.simonichknives.com
 
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